The present invention is related to storage media. More particularly, the present invention is related to limited play storage media.
Optical, magnetic and magneto-optic media are primary sources of high performance storage technology which enables high storage capacity coupled with a reasonable price per megabyte of storage. Use of optical media has become widespread in audio, video, and computer data applications in such formats as compact disc (CD), digital versatile disc (DVD) including multi-layer structures like DVD-5, DVD-9, and multi-sided formats such as DVD-10, and DVD-18, magneto-optical disc (MO), and other write-once and re-writable formats such as CD-R, CD-RW, DVD-R, DVD-RW, DVD+RW, DVD-RAM, and the like, hereinafter collectively “data storage media”. In these formats, data are encoded onto a substrate into a digital data series. In pre-recorded media for optical media, such as CD, the data are typically pits and grooves formed on the surface of a plastic substrate through a method such as injection molding, stamping or the like.
In some applications, it is desirable to have a limited life for an optical disc. For example, sample computer programs are provided to potential customers in order to entice them to purchase the software. The programs are intended to be used for a limited period of time. Additionally, music and movies are currently rented for a limited time period. In each of these applications and others, when that time has expired, the disc must be returned. A need exists for machine-readable optical discs that do not need to be returned at the end of a rental period. Limited-play discs provide a solution to this problem.
Limited play discs have been produced in various fashions. One method comprised forming a disc where the reflective layer is protected with a porous layer such that the reflective layer becomes oxidized over a pre-determined period of time. Once the reflective layer attains a certain level of oxidation, the disc is no longer readable. The problem with this and other limited play techniques is that these techniques are defeatable. If the method for providing limited play to optical discs can be easily defeated by a customer or a cottage industry, discs would no longer be “limited-play”. In the case of a coating or material rendering an optical disc unplayable, for example, facile removal or modification of that coating and/or material could provide a disc with unlimited playability.
There is a great desire on the part of movie studios to protect their intellectual property. Commercialization of limited-play data storage media that can be easily defeated to afford data storage media with unlimited playability would present an unacceptable risk of losing intellectual property.